Mercury removal units utilizing adsorption beds are used in cryogenic gas plants, such as natural gas liquids (NGL) recovery and liquified natural gas (LNG) production plants, to remove mercury from a feed gas, e.g., natural gas. Mercury must be removed to prevent damage to aluminum heat exchangers. Mercury removal beds are dehydrated using hot, dry gas, which can be sourced from nitrogen or process gas downstream of a molecular sieve dehydration unit in the cryogenic gas plant, in which water is adsorbed onto molecular sieve material. The hot, dry gas flows through the mercury removal bed to desorb water from the mercury adsorbent material. The spent, wet gas from the mercury removal bed is typically sent to flare, rather than being recovered. This results in significant costs associated with unrecovered nitrogen or process gas, as well as undesirable environmental impacts and potential financial penalties associated with flaring.
It would be desirable to have a system for dehydrating mercury removal beds resulting in cost savings and reduced environmental impact.